Radio receiving system



Nov.- 7, 1933.

A. Gr D. WEST RADIO RECEIVING SYSTEM Filed.July 30, 1931 INVENTOR. Arthur Gilb erLD ixonWest,

A TT ORA/ Y.

Patented Nov. 7, 1933 PATENT 1,933,778 1 p v RADIO RECEIVING SYSTEM Arthur Gilbert Dixn-West,-Beckenharn, England Application July 30, 1931, Serial No. 553,934, and

in Great Britain August 21, 1930 v 14 Claims. (01'. 250-40) The present invention relates to supersonic heterodyne radio receiving systems.

It is well known that when sucha receiver is tuned for the most efiicient reception of any par-,

ticular signal, a definite relation should exist between the resonance frequencies of the aerial or signal input circuit or circuits, the local oscillator circuit, and the tuned circuits or circuits of the intermediate frequency amplifier, the latter being in tuned usually to a fixed frequency. If however, it

' is desired to vary also the intermediate frequency circuits for wide wave length range of tuning with proper selectivity and image frequency re jection and if L101, LzCz, and LsCs represent re- 1,5 spectively, the inductance and capacity in these circuits, this completely variable relation can be expressed by the equation This expresses in an obvious form the condition that the sum or difference of the frequencies of the input and oscillator circuits must equal 5 the frequency of the intermediate circuit, which is the relation necessary for superheterodyne operation. It should be noted that according to this invention C1, C2 and C3 are all simultaneous,- ly variable and substantially equal incapacity value throughout a predetermined variable tuning range.

It is very desirable that the condensers en ployed for tuning all of the above mentioned resonant circuits should be ganged or, operable from a single control, in order to make this possible, and at the same time to satisfy the above equation for all positions of the tun ing control, it has beenproposed to make the inductancesin the circuits equal to one another,

so that L1=L2=L3, and to so arrange the movable plates of the condensers with respect to one another, that. with allconderisers variable the relation I cuits tuned to electrical currents at differing frequencies wherein the use of condensers of the straight line frequency type is not essential.

'The invention Willbe better understood from the following description, when taken in con-- nec'tion with the accompanying drawing, and its scope will be pointed out "in the appended claims. In the drawing, the figure is a schematiccircuit diagram of a portion of a superheterodyne radio receiver embodying the invention.

Referring to :the drawing, in accordancewith a the present invention, in asuperheterodyne receiver 5 in which the antenna or radio frequency input circuit 6, the local oscillator circuit fl and an intermediatefrequency circuit 8 are tuned by means of condensers 9, 10, and 11, respectively, operated by means of a single control member 12, the effective values of the inductance of the coils 13, 14 and 15 in said circuits are chosen so as to "substantially satisfy adefinite relation, this 'relation being expressed by the equation derived from Equation (1) when"C1=C2 Cs l l 1 v al v as Where L1, L2, and L3 or L2, L3 and L1 may represent so the said effectivevalues of the coils 13, 14 and 15 in said input, local oscillation and intermediate frequency circuits, respectively.

In the above equation, since the condenser values are all assumed to be'equal at any position throughout the tuning range it will be seenthat Equation (2). is derived from Equation (1) by removing therefrom the fixed values and retaining therein only the variables, which is possible under the condition of operation assumed. 90,

The basic idea underlying the invention is to utilize an ordinary ganged condenser for the purpose of tuning input, oscillatorand intermediate circuits of a superheterodyne receiver. Accordingly,!an'y ganged condenser in which theindividual sections are accurately matched may be used, each gang having any convenient capacity value'and plate shape. The choice of values for the inductances of the three circuits is governed by Equation (2) and any convenient values 1 may be given to two of the inductances, the third being chosen to enable the equation to be satisfied. Thus for exampleL1: 0O microhenries and L3=1o,oc0 microhenries; L2 may have a value of either 105.5 orv 94.5 microhenries. L1 should preferably be chosen to give'the required tuning range and L3 should be as large as possible to give a low frequency for the intermediate amplification.

In the present example, the antenna or radio divider resistor 25.

frequency circuit 6 is energized with signal currents through the inductance 13 from a suitable coupling coil 16 associated with said inductance and connected with an antenna 17 and ground 18 as a source of radio frequency or other signals.

As has been pointed out above, if a ganged condenser in which C1=C2=C3 over the entire range of variation, and further, if the inductances of the three coils satisfy Equation .(2), then the aerial or radio frequency oscillator and'intermediate circuits will maintain the superheterodyne relation for all frequencies to which the receiver is tunable.

It is, of course to be understood that the effective values of the inductance in the circuits, though largely determined by the coils themselves, are also influenced by the coupling existing between the coils and other circuit components.

The antenna or input circuit 6 is directly connected with a detector or frequency changer tube 19 which in turn is coupled with the intermediate frequency circuit 8 by a suitable coupling coil 20 in the detector output circuit 21 associated with the inductance 15.

An intermediate frequency amplifier tube 22 is connected with the intermediate frequency circuit 8 as indicated and is provided with output terminals 23 which may be connected with other apparatus (not shown) forming part of the receiver, as is well known;

The local oscillator circuit 7 connected with an oscillator tube 24 as a source of oscillations, and the inductances 13 and 14 are coupled as indicated'as a means for transferring the oscillations to the frequency changer or detector tube 19. A suitable source of anode potential for the tubes is indicated by the tapped potential Other circuit details do not concernv the invention and accordingly are not described.

It is clear that the only other condition necessary, in order that Equation (1) should be satisfied for all positions of the tuning control, is that C1=C2=C3; that is to say, the capacities of the tuning condensers should equal one another at all positions of the tuning control.

Thus in a supersonic heterodyne receiver having its inductance coils which may be of any suitable type, so wound that their values satisfy Equation (2), the tuning of the oscillatory circuits may be effected by any system of ganged condenser, such for example as are used in tunintermediate frequency,

ing the circuits of a thermionic amplifier for high frequency electrical oscillations.

The advantage in tuning all circuits, including the intermediate frequency amplifier is, primarily, the reduction of the image frequency response in the higher frequency range of operation wherein the selectivity is normally reduced, as is well known. By tuning the intermediate frequency circuits, thereby providing for a variable a desired image frequency separation may be maintained throughout the tuning range.

It will be seen that the intermediate frequency circuit is variably tuned simultaneously with the input or radio frequency circuit. This arrangement has the further advantage that the intermediate frequency may be made low at one end of the range, as is desirable to reduce the tendency of generated harmonics to be fed back to the input. However, as is wellknown, for the purpose of preventing image frequency response, the intermediate frequency should preferably be high and it will further be seen that by the tuning arrangement provided, this desired result is obtained at the other end of the range, to which, under present conditions, the majority of broadcasting stations are allocated.

I claim as my invention:

, 1. In a radio receiving apparatus of the heterodyne type, the combination of tunedresonant scillator circuit, a tuned resonant intermediate frequency circuit, a tuned resonant input circuit, and means for simultaneously changing the resonance points of each of said tuned circuits.

2. In a radio receiving apparatus of the heterodyne type, the combination of an oscillator circuit including a tuning inductance, an intermediate frequency circuit including a second tuning inductance, and means including a tuning condenser associated with each of said inductances for simultaneously tuning each of said circuits, said condensers being of substantially equal capacity.

3. Ina radio receiving apparatus of the heterodyne type, the combination of an oscillator circuit including a tuning inductance, an intermediate frequency circuit including a second tuning inductance, a signal input circuit including a third tuning inductance, and a variable con denser having substantially duplicate condenser sections one of which isconnected with each of said inductances and arranged for simultaneously tuning said circuits. I

4. In a superheterodyne receiver, the combination of a signal input circuit, a local oscillator circuit, and an intermediate frequency circuit, an inductance and a condenser connected in each of said circuits to provide a tuning means therefor, said condensers being adjustable to substantially equal capacity values and the inductances in the, input, oscillator and intermediate frequency circuits having values which satisfy an equation 1 1 l 1/ l w 2 1/ 3 in which L1, L2, and L3 represent the values of said inductances.

5. A superheterodyne radio receiving apparatus having a signal input circuit, an oscillator circuit and an intermediate frequency circuit, a tuning inductance in each of said circuits, said in ductances being related in value to each other in accordance with the formula said inductances in the'input, local oscillator and intermediate frequency circuits respectively, and means for varying the capacity to substantially the same value in each circuit.

6. A superheterodyne radio receiving apparatus having a tuned signal input circuit, a tuned oscillator circuit and a tuned intermediate frequency circuit, the inductance values of said tuned circuits being related to each other in accordance with the formula m ls;

1/ 1 1/ 2 1/ in which L1, L2, and L3 represent said inductance values of the input, local oscillator and intermediate frequency circuits respectively, and a gang type variable condenser having duplicate units one in each circuit, for simultaneously tuning said circuits.

7. A superheterodyne radio receiving apparatus having a signal input circuit, an oscillator circuit and an intermediate frequency circuit, a tuning inductance in each of said circuits, said inductances being related in value to each other in accordance with the formula 1 1 w z w s in which L1, L2, and L3 represent the values of said inductances in the input, local oscillator and intermediate frequency circuits respectively, a variable tuning condenser in each of said circuits, and means for simultaneously operating said condensers, said condensers being thereby adjustable to substantially the same capacity for each position of adjustment of the movable control means.

8. In a radio receiving apparatus of the heterodyne type, the combination of a signal input circuit including a tuning inductance, an oscillator circuit including a second tuning inductance, an intermediate frequency circuit including a third tuning inductance, a variable gang condenser having duplicate condenser sections, one of which is connected with each of said inductances for simultaneously tuning said circuits, the values of said inductances being arranged in accordance with the equation 1 1 w 1 1/ 2 w s in which L1, L2, and L3 represent the values of the first, second and third named inductances respectively.

9. A superheterodyne receiver having three tuned circuits, an oscillator connected with one of said circuits, an intermediate frequency amplifier connected with another of said circuits, means for applying signal energy to another of said circuits, means including an inductance and a condenser in each circuit for simultaneously tuning said circuits, the inductances in each of said circuits being related to each other in accordance with the formula odyne type, the combination of a plurality of tuned resonant circuits, an oscillator connectedwith one of said circuits, an intermediate frequency, amplifier connected with another of said circuits, and means including a variable tuning condenser in each of said circuits for simultaneously tuning said circuits to predetermined frequencies, said condensers being interconnected for unitary control throughout a predetermined tuning range of operation and being adapted to provide equal capacity values one with respect to the other for any adjustment throughout said range of operation.

11. In a radio receiving apparatus of the heterodyne type, the combination of a tuned resonant oscillator circuit, a tuned resonant intermediate frequency circuit, and means including a variable tuning condenser in each of said circuits for simultaneously changing the resonance point of each of said tuned circuits, said condensers being interconnected for unitary control throughout a predetermined tuning range of operation and being adapted to provide equal capacity values, one with respect to the other, for any adjustment throughout said range of operation.

12. In a radio receiving apparatus of the heterodyne type, the combination of a tuned resonant oscillator circuit, a tuned resonant intermediate frequency circuit, a tuned resonant input circuit, and means including a variable tuning condenser in each of said circuits for simultaneously changing the resonance points of each of said tuned circuits, said condensers being interconnected for unitarycontrol throughout a predetermined tuning range of operation and being adapted to provide equal capacity values, one with respect to the other, for any adjustment throughout said range of operation.

13. A heterodyne radio receiving system having an intermediate frequency amplifying circuit and an oscillator circuit, characterized by the fact that unicontrol means are provided for simultaneously tuning said circuits through differing predetermined frequency ranges.

14. A heterodyne radio receiving system having an intermediate frequency amplifying circuit and an oscillator circuit, characterized by the fact that said circuits are simultaneously tunable through differing predetermined frequency ranges and that the tuning means therefor includes a ganged variable condenser having substantially duplicate units one in each of said circuits.

ARTHUR GILBERT DIXON WEST. 

